Telephone system



April 7, 192 s. 1,532,652

H. D. CURRIER ET AL TELEPHONE SYSTEM Filed Sept. 18, 1920 2 Shuts-Sheet 1 t I mill-m5; 5211.121

H. D. CURRIER ET AL Ami 7, 1925. 1,532,652

TELEPHONE SYSTEM Filed Sept. 18, 1920 2 Shuts-Shut 2 7 V r i tree STTES o-Js-srris Al-JDVJI sees swrrorrsossn PGATIGN or ILLINUIS.

Application me re, Hiram D; CURRIER Snore, citizens oi itlie erios residing Chi- 1a,. field State of 111i? hit 5' cert-sinner; end use? p o 7 'Telephone Systems, 11 t e speoifiostion.

rteiephene systems uhirly Wlilliilllzllai private. branch e:;--

loos private; branch e3:-

"iitiois and manual exchanges exchanges.

our invention thepror s whereby the private by th use ofzz e e the. automatic 6X6 to the \iliIIQC i called line without the mg of the trunk circuit belngili'l a local hne .i

- a e of our inventionis the c actuate the central offie with the plug of the local subscribers line e local subscriber has circuit to clear the hire through to the main exchenge so r seorld the pri'va e branch siibsorlber s-tin remove his is removed: from the local jack, the" a; will again be seized and extendthe eetion through to the main exehienre,

1 the event that the p'rivetebranch 5e substation is equipped with lle Vlu deriu, the subscriber may again actuate the eutonia o apparatus to" seize another as Wanted. In theevent that celled liiie the trunk circuit was used to extend commotion to a main manual exchange,

\T the private branch exchange suh- 'es his receiver the trunk is ed to do said ineizi hene'e exehen 'e operator s of our invention is thewhich the trunk circuits.-

vi r po itionenu iL-Cuhbeing connected Ly the hes A is;

', ILLBZNGIS, i

Serial 7330.: l -11,289.

provision of'ni'eens thetiefterthe private: branch exchange ssbseriher: heegs up andi clears the trunk to. the should another rage lee.-

ll; leiiip V "'etendir T on inve 101i, 'reIerenee-niey he'hed tothe s=3-- ur invention; and

Fig. isa sliele disgraininetio circuit srre g'eineit strsting the stapes bility of i ri'ivention to an automatic QX- 75 in general to our in F153;. 1, I Show a telling s bstation A terminating at the I in icrche Age M i=1 a. line oircuit B, cos-- 80 prising the usual lire relay LR out-oil relay CO, line signal L and the multiple ache J; V i

The cor-l circuit C located at the main eXchu-nge'M is sh wn f0" use in exten connections from the circuit comprises an answering plug" 3* ing plug UP, the two plugs viiy ors tho said conductors i densors K and K interposed t societed with the answering} en iieuit G is the answering tip supervi elziy AT and an answering; sleeve Visory relay AS, the two re eys centre the illiSVFGlllg' supervisory le np s eizited With-the calling end of the c circuit n is a calling tip supervisory 1 CT and a calling sleeve supervisor US, the two relays controlling the o.

supervisory lamp CL. A listening hey is also shown vhieh when setusted connect-s the operators set to the cont duct-ore. Airinging key 11;;

which, when actuated, connects the ringing generator G to ring the call bell ot the called-tor line, or to the trunk circuit.

The calling plug CP is adapted for connection to the multiple jacks of other telephone lines terminating at the switchboard in the same exchange, or for connection to the trunk jacks TJ which are located at the operators position, and which are terminals of trunk circuits PC. The trunk circuits PC extend to a private branch exchange switchboard PB, and the said jacks TJ are connected to the said trunk circuits PC, which terminate at the private branch exchange PB over the heavily marked conductors ant l2.

The private branch exchange trunk PC is provided with a. ring-up relay RU, which relay operates when ringing current is applied troin a distant exchange. The ring-up relay RU, upon energization, brings about the lighting of the line lamp LL, to notify the operator at the private branch exchange board that a call awaits her attention. A listening key LK is provided which, when actuated, connects the operators set 0 to the trunk conductors for the usual purposes. A combined disconnect and guard relay DS is also provided which is energized upon the actuation of the listening hey LK to bring about the eliaceinent of the line signal LS when the operator answers the call. A sleeve relay SL is also provided, which relay is energized when the operator inserts the trunk plug TP into the local line jack J of the wanted station at the private branch exchange. A ringing key Eli is also provided which, when actuated, connects ringing generator G to signal the called-tor station at the private branch exchange. A supervisory relay SR is also provided which is energized when the party at the called private branch exchange substation answers. A holding relay a9 is also provided, which energizes upon the energization of the supervisory relay SE to bring about the eitacement of the holding lamp HL and also disconnects the holding coil HC from across the trunk conductors, the said holding coil being bridged across the trunk conductors upon the energization of the relay B5. A disconnect signal DSL is also provided "for the usual disconnect signaling purposes. An operators disconnect relay 92 and a trunk cut-oii relay COP are provided and are brought into operation in connection with the trunk circuit PC when the private branch exchange operator O is extending a connection from the local private branch xchange substation to an automatic main exchange. A calling device CD is also provided which is used by the operator in extending a connection to a main automatic exchange. A night jack NJ is also provided for the usual purposes. To the right of the private branch exchange trunk PC I show a local private branch exchange substation F, terminating thereat in the jack J, a line relay LE and a line signal L.

In Fig. 2 we illustrate a modified form of trunk circuit in which, upon the energization of a relay of ie trunk circuit PC after the branch exchange subscriber replaces his receiver and wishes to recall, the removal of the receiver brings about the lighting of the line lamp to notify the operator that the local subscriber wishes to recall. The trunk circuit PC is provided with apparatus similar to that mentioned in connection with the trunk circuit PC of Fig. 1.

Having described in general the apparatus which embodies our invention, we will now describe more in detail the operation 01": the system as illustrated.

Assuming new that the subscriber at the substation A at the main exchange initiates a call, the removal of the receiver at the substation closes an energizing circuit for line relay LR of the sol scribers associated line circuit B, and the said relay LR, upon energization, closes its alternate contact, establishing a circuit through the line lamp L,

which lamp L is now lighted. The operator at the main exchange noting the lighted line signal L inserts the answering plug AP of one of her cord circuits G into the answering jack 5 oi the calling line A, and the insertion of the said plug AP establishes a series energizing circuit for the answering supervisory relay AS of the cord 0 and the cut-off relay CO of the line circuit L, traced from battery through the winding of the relay sleeve contacts or" the connected plug AP and jaclr J to ground through the windor' the cut-oft relay CO. The relay Ct upon energization opens the energizing circuit oi' the line relay LR, which relay LR now restores and eii'aces the line signal L. The answering tip supervisory relay AT is also energized over the line to prevent the premature lighting of the answering supervisory lamp A The operator of the cord circuit C now actuates her listening key LK to connect her operators set 0 to the cord conductors and inquires the wants of the calling subscriber at the substation A.

Assuming that it is the subscriber i lo cated at the private branch cxchang calling plug GP into a trunk jack TJ ing to the private branch exchange In) which the subscriber is located. The

sertion of the said plrg Cl? into the acl:

no callground. The closing of alternate Contact 3 of the relay CS closes c. ()1 'cuit for the celltl e ing of the .saitlllenip 65% co; to, normal contact 31 oiithe in CT to ground,

circuit. L over the t unl; contluc l-Q ting'iiiu DU, con or 09, nor no dial relay 1 t trunk ccnclu-t tenta le of the GP to battery and contact of the 'ringin osing ot alte'nete cone J close: an energizing circuit oit th Y 2 LL from battery through the lamp 3c enn-tied alternate contu t of l The operator noting the lighted L ROW zictuetes her listening he closure of alternate contact l'ey LII establishes an energizl'or the cliscoi t t iroig 21y DE contlu a l of listen normal contact to ground at n gino "0y BK. ontett of key "I or the holding; i cry through the sell lamp t ct ll ot' key L tact of relay 9, conduct-o1 nor-incl contact 01 or r If the Call pro lzn the operator, the circn the operator the branch e1 the ringing lie Eli, which op relay BS and allows it to r store relay DS upon energizin alterne ontzict of the l the to c el all Wing it to restore to ctlece the l, 1 LL. The relay DS new closes :1 circuit for itself from battery t T0037 windin i's alternate connorm ill conrelay BS biiclges'the holding coil 11C across the trunk conductors f .Ol11 tl1"30ln" 5 conductor 35, through the holcli coil ll, normal contu r'ele' across the trunk conductors the relay \J the cord circuit C at the main exchange "1J6? ates to openits normal contec 3i, t ing the circuit of the calling on lamp Clito the the soitllazn notify th operator at the 11 1' that the operator Assuming th i (i change stetiol and this inscrt'or energmmg circui traced :rm hatte V 3 the seen in 1 BS, condo; ilug' to ground. l. The relay 81,! upon u closes its alterr c ntzicts thereby closing; the tri to the called suhsta The closi v ilteinelc contact 6% ie sleeve relay SL multiples the groun us he sleeve of the jack o to ie r BS, this multiple ground connection to the being ti2.C iflOlD. battery through no incli oi? the relay BS, conductors s entl to, alternate contact of relay contltlCtOl 66, normal contact 6? oi 1' hi condoctor 01, through the sleet 1 le 5 l on conductors 5, ellcrn of ieliiy S2, tor GS of of relay i uctor "l plug '1? t t the sle J. the said ll up hill rein until the soy scriher i answers.

The operator now actuates the ringing key BK to connect generator G to signal the callecl-t'or-station F, the ringing circuit being traced from the ungrountletl pole of the generator G, tip contacts'of the plug TP and the ackJ throu 'h the condenser and cell bell of the called station F, the ring contacts of the jack J and plug TP, through the alternatecontact of the ringing key BK to battery and ground.

The opening of normal Contact 51 of the ringing key BK opens the lo king circuit of the role} DS, but clue to the fact that the ground from the sleeve 01" the jack J is also multipled through the upper Winding of the relay DS, as justdescribecl, the re- LIX lay remains energized during the time that the ringing key is actuated. The party at the station F, in response to his call signal, removes his receiver from the switchhoolr, bringing about the energization of the supervisory relay SE. The circuit tor relay SR extends over the called line F.

The closing of alternate contact ot the supervisory relay establishes an energizing circuit for the relay ll), traced from battery through the upper winding of the relay 49, conductor '41, through the lower winding of the relay DS, conductor 72, alternate contact 70 of the relay Sit, conductor 61, through the sleeve contact of the trunk plug TP to ground at the sleeve of the jack J. The opening of normal contacts as and 67 er the relay 4C9 opens the locking circuit through the upper winding of the relay DS, but the series ener izing circuit through the upper winding 01 relay 49 and the lower winding of relay DS permits the continued eners -ization of the said relay DS. The opening of normal contact 56 of the relay 49 also removes the holding coil HG from across the trunlr conductors. The closing of alternate contact 6? of the relay ea establishes a locking circuit for relay a9 traced from battery, through the resistance and the lower winding of the relay 49, alternate contact 67 oi the relay 4L9, conductor ()1, through the sleeve of the trunk plug T1 to ground at the sleeve of the jack J. The opening of normal contact 67 of relay 49 opens the energizing circuit-of lamp HL, which is now eliaced, and notifies the operator at the private branch exchange PB that the party the privatebranch substation F has answeredv The subscriber A at the main exchange and the party at station F of the private b anch exchange are now in conversational circuit. The said talking circuit may be traced over the heavily marked conductors.

Assuming'that the subscriber at substation A and the party at the private branch exchange st tion F have finished conversation, the restoration of the receiver at the station F of the private branch exchange opens the energizing circuit of the supervisory relay SR, and the opening of alternate contact 70 of the said relay SR interrupts the ground connection from the sleeve of tie jack J, and the relay DS thus restores to normal. The relay-D55 upon deenergization opens its alternate contact 60, which opens the energizing circuit of the sleeve relay SL, which relay restores. The opening of its alternate contacts 62 and 63 interrupts the trunk conductors. The closing or" its normal contacts 76 and 77 places the local private branch exchange battery upon the trunk conductors, extending to the substation.

The closing of normal contact 70 of the sleeve relay SR now closes an energizing circuit for the disconnect signal DSL, traced from battery through the filament oi the said disconnect signal DSL, alternate contact F8 or the relay 49, conductor 79, normal contact 70 of the relay Slit, condue tor 61, through the sleeve of the trunk plug T? to ground at the sleeve of the jack J. The disconnect signal lighting notifies the private branch exchange operator that the subscriber has replaced his receiver upon the switchhoolr.

The relay 49 remaining energized to ground at the sleeve of the jaclr J through loclring contact 67, prevents the holding coil HG from being bridged across the trunk conductors, and the calling tip supervisory relay CT of the cord circuit C is thus ale-energized and upon restoration its normal contact 31 is again closed to light the calling supervisory lamp CL, vhich lighted signal CL notifies the main exchange operator that the private branch exchange station F has replaced his receiver. lhe subscriber at the main exchange substation A replacing his receiver, opens the circuit through the answering tip supervisory relay AL, which relay upon restoration closes acircuit through the answering supervisory lat: p AL, which lamp AL is lighted to no y the operator that the subscriber at substation A has replaced his receiver. The operator at the main exchange noting the two lighted signals AL and CL now with draws the answering plug AP and calling plug Cl from the respective jac {S J and TJ to open the circuits of relays AS and of the cord circuit C, which relays AS and CS upon de-energization etlace the su pervisory signals AL and CL. Relays CG and CG also restore, thus placing the apparatus at the main exchange in condition for use in establishing other connections. The private branch exchange operator at PC, noting the lighted disconnect signal DSL, withdraws the trunk plug TP from the jack J, which opens the locking circuit of the relay The relay 49 upon ce-energization restores and opens its alternate contact 78 to erlace the disconnect signal DSL. The private branch exchange trunk circuit PT is now at normal and available for in establishing other connections.

Assuming now that the subscribers have replaced their respective receivers upon their respective switchhoolrs and tnat the party at the private branch exchange substation l1" again removes his receiver before the trunk plug T? has been removed irom the jack ll. this removal of the receiver brings about the energization of supervisory relay Sit, traced from battery tirough normal contact 77 of sleeve relay SL through the winding of said relay Sit, ring contacts of the connected plug TP and jack 5 through the closed contacts ofthe substation switchhook, bacx through the tip conxicts of the connected plug TP and aclr J to ground at normal contact 76 role; bill. The relay upon energization closes its alternate contact 2 0, establishing an energizing circuit for the relay DS, traced from bait through the upper winding of relay all), conductor '71 through th lower Winding of relay conductor 72, alternate contact 70 of relay SR, conductor 61, through the sleere oi the plug TP to ground at the sleeve of the jack The relay upon energization closes its alternate contact 60, es tablishing an energizing circuit for the sleeve relay Elli, traced from battery througl'i the winding of relay conductor 53, alternate contact 60 of relay ES, conductor 61, sleeve cont-act of the plug T? to ground at the slee're oi Ll-O jack J. The relay SL-upo'n energization closes its alternate contacts 62 and and thus extends the station F at the private branch exchange PR to main exchange, the main excaange "attery thus holding; the relay SE nergized. The line relay LR at the main exchange will now op crate, providing the plug GP has been with drawn "from the jack, over a circ it traced from battery through the Winding of relay lllt. normal contact- 80 relay CO, conductor 32, normal contacts and 34-, alternate contact 621d relay Elli, tip contacts of the plug T? and jacl J, th 'ough theclo'sed contacts ot' the substation i ring contacts of th jack J and plug Tl through the of relay alternate contact 63 SL, normal contacts to and 41, conthe trunk signal TS, which notifies the operator at the main exchange that a private branch exchange station is calling. The r .av SR upon energization also opens the circuit of the disconnect signal DEL, Which also gives the private branch exchange operator an indication that the party at the station has called. The closing of contact 800 of key LK when the operator, for any reason, actuates the key Ll? while the plug Tl? is in jack J, after the subscribers have replaced their receivers, operates to shunt out relay 49. thereby ole-energizing the same.

Assuming that the subscribers have replaced their receivers and the operator at the main exchange desires to extendanother call to the branch exchange before the plug T? is taken (lOWn, the main exchange operate applies ringing current to the trunk and operates the relay EU as before d. causing the lamp LL to glow, tying the private branch exchange o it another call is being extended a branch exchange. The operator again operates her listening lze'y and completes the to ground at normal contact 81 o to light tact 51 0 5 the ringing connection. .The ringing current applied to the 'trun. circuit bythe main exchange operator did not reach the substationl even thou h the plug Tl nns in the jack J, for the reason'tl at the trunk circuit Was open at con acts 62 and 63 of relay SL.

The branch exchange operator may extend a connection to the main exchange by operating her listening key, even though the trunk plug T? is not in a aclr.

Assuming now that a call is extended from 'an automatic exchange to the private branch exchange PB, the ringing current which is applied from the automatic exchange operates the ring-up relay BU of the branch exchange trunk PC, which -wasseized by theconnector of the automatic exchange, and the operation of the trunk circuit PC is the same as that described inconnection with a manual connection, as just described.

When the trunk circuit is used in connection with a main automatic exchange, it may terminate the main automatic exchange in line switch of the usual type and in the banks or rotary connectors or straight line connectors such as is described and illustrated in the United States Patent No. Lll l-Jl. issued August 15, 1916, to Harry H. Ide. In this case the conductors 32 and 4:2 leading to the main exchange Will not be included in he apparatus, the trunk circuit being connected directly to the conductors leading to the-automatic exchange, and, therefore, the operation or" the trunk circuit at the branch exchange will not affect the apparatus at the manual main exchange.

The operation of the trunk PC when a pri rte branch station calls a main change subscriber of an automatic exchange, is follows: Assuming noW that theoperator at the private branch exchange PC Wishes to extend a connection to a subscriber at an automatic exchange, she actuates her listening key LK, which closes'a circuit for the disconnect relay DS, traced from battery through the upper Winding of the relay DS, conductors and'4l6. alternate Contact of the listening hey LK, conductor 47, normal contact 48 of relay 4:9, conductor 50 to ground at normal conlrey BK. The closing of. alternate contact 38, upon the energization of DS, bridges the holding coil HG across the trunk conductors, as previously described, thus operating a'switch to connect the trunk to either a SClOCtOT-FfiflfCll or a connector switch, depending upon the size of the exchange. The operator now operates her callingdevice CD to send the required number of impulses to operate the and remain closed until the dial returns to normal after having transmitted its first set of impulses. The closing of shunt springs and 91 establishes an energizing circuit for the relay 92 associated with the operators set troin'battery through the winding of relay 92, conductor 933, closed shunt springs 90 and. 01, conductor 9- to ground at alternate contact 95 of the listening key K The relay 92 upon cnergization closes its alternate contacts 96 and 97 and bridges the condenser 98 across the trunk conductors over conductors 99 and 100, and through alternate contacts 101 and 102 of the listening hey 114K to the trunl: conductors. The closing of alternate contact 103 of the relay 92, also establishes an energizing circuit for the trunk cut-off relay COB, traced -from battery through the winding of said relay CQR, conductor 10 i, alternate contact 105 of the listening key Til; conductor 100, alternate contact 103 of relay 92, conductors 107 and .3, closed contacts 90 and 91, conductor 9-l to ground at alternate contact 95 of listening key Ll'i. The relay COP. upon cnergization closes its alternate contacts 108 and 109 and disconnects the trunk apparatus and now extends the dial contacts 110 and 11.1 over conductors 112 and 113, through alternate contacts 108 and 109 to the trunk conductors. Che impulses from the calling device now transmitte,

ver the trunk conductors, and at the first ret of impulses the dial restores to normal, and upon said restoration the shunt contacts 90 and 91 are opened, and this removes the ground connection. extending from alternate Contact 95 of listening key LEI from relay COR and relay 92 asso ciated with the trunlr operators set. Relay CGR being a quick-acting relay, restores before relay 92, due to its slow-to-release construction, and the said relay 92 is momentarily held energized and the condenser 98 bridged across the trunk conductors through alternate contacts 96 and 97 of relay 92 to take up the discharge from the line so as to overcome the discharge into the operators set. it the beginning of each set of impulses the shunt contacts 90 and 91 are closed to energize relays COR and 92, and utter each set of impulses, relays CUR and 92 deenergize for purposes as just described. After the last set of impulses, relays COR and 92 (lo-energize due to the opening or shunt springs 90 and 91, and the operators set G is now connected to the trunl: conductors through normal contacts 90 and 97 of relay 92 and alternate contacts 101 and 102 of the listening key Lil. The re lay DS is held energized due to the closing of contact 44 of the listening key LK and locked up through its alternate contact52 as already described. The holding coil HC is bridged. across the trunk conductors upon the closure of alternate contact 38 of relay D3 to hold the apparatus at the automatic exchange in its actuated position. The operators set U being bridged across the trunk conductors, she may now converse with the called subscriber at the main exchange, and to connect the said subscriber with the station ll, she' inserts the tru ll; plug Tl into the jaclr J ot the station F and the operation of the apparatus of the trunk circuit PC is the same as prcvioualy described. 'When the party at the station F answers, the apparatus is held in its operative position, through the now closed switchhook contacts. Upon termination otconversation and when the party at substation F replaces his receiver the opening of the switchhock contacts opens the circuit of the apparatus at the automatic exchange, bringing about the restoration of the said apparatus, as is well understood, it such apparatus is of the type that is restored by the calling subscriber. The trunk circuit is cleareo. as before mentioned so that it may be used for further calls.

Should the party at the station F call, the operator would insert the trunk plug into the jack J, and now should the operator dial out to select a substation at'a inain automatic exchange, the relays DS, SE, SE; a lid el9 will be operated, but during the dialing operation relay COR is energized and relay SR restores, having its battery circuit opened at contacts 3st and 10 of relay COR, but relays DS, SL and will remain energized over circuits as previously described. The relays GOP. and 92 energize and de-energize, as previously described, before and after each set of impulses, and the condenser bridged across the trunl; conductors takes up the surge of the line battery due to the energization and de-energization of relay COR, thus something out the make and break wave of the battery through the sub station F. The operator can dial with the plug Tl? in the ack J and the receiver on or oil the hook at the substation.

Assuming that the private exchange sulr station F is provided with a calling device X, when the trunk circuit is connected to the jack J relays SR. SL, DS and 4:9 are operated to extend the subscriber's line through to the main exchange. The subscriber F operating his calling device 1*; opens and closes the trunk circuit, thereby operating the automatic switches at the main exchange. the impulses and open the circuit of relay DS, but this relay is sufficiently slowact ing to remain energized during the impulsing. hen the subscriber F replaces his receiver, he releases the automatic equipment and clears out the trunk circuit PG.

Referring now to Fig. 2, we illustratea modified form of our invention whereby The relay SR may follow .t J11 1 current 1101! when the subscriber at the substation F of the private branch eXcliange-replaces hls receiver, the energizing of a relay brings When Ti is r.'-'ithdra .vn from the local aclrll he nninci enabled to'signa the operc at tl which the trunk r terminates.

priratebran 1 exchange, PB; the ringing 1 1e inain exchange extends over ,dLct'ors, through normal cont 1.50 of ie relay COR, conductor 151, 1 'ough the winding of said relay RU, o n'ial contact 152 of relay DS', conductor normal contact 151- of relay C911, 1 there back to the main exchange. Re- RU upon energization closes its altereitact 155, which closes an energizing t for the'line lan'ip LL of the private exchange trunk PC, from ground through alternate contact 155' of relay RU, concrctor 56, through the lamp LL to battery.

The operator atthe private branch er.- angg'e circuit PC noting the lighted line gnal LL now actuates her listening key to co1.necther operators set to the COIEQHCtOlSL The closing of alternate contact 157 of the listening key LK closes an energizing circuit for the relay D traced from battery through the lower Win 21 of the relay DS'r, conductor 158 alterntact 157 of the listening lrey' LK or 159, normal contact 160 of the 7 1., connector 162 to "ground at of the ringing lrey .snre of alternate contact 152 0;

l bridgesthe holding'coil t ink conductors for purposes a the trunk 001 L1 Ll alternate contact 164, nori'nal contact 160 of i at normal contact 163 of the ringing key REP. r T upon energization unlatches jack J of the local line. Upon the insertion oi the trun plug TP into the jack J permanent gr and upon the sleeve of the jack J new extends through the sleeve of the trnnl: plug Tl, over'eonductor 165;

1 re main exchange in equip-- rnent similar to that shown in Fig. 1, in-

Assuinv in now that the call is extended to thehe r s, 1. l described in connection with Fig. the closing of alternate contact 161 of the relay DS closes the lOCklDg CHIC-flit for the relay DSC traced from hatter tllYOlIlpIll the upper Winding of the said relay D5 thro 'gh normal contact 166' of re1ay'i61,

conductor 158, through the lower Winding o the US" to battery. This ground through the 'lowr Winding of the relay BS holds the said relay BS energized when the ringing key I is An energizctuated. ni cr'cint for the holding signal ill] isclosed, the circ ,it heing'traccd fron .tt, 1 thr ah the rolling signal EL l t tor 158 'ner2nal con ct 166 of n I conductor 165, the slee *e of th Tl to ground at the sleeve '0; lainp HL the subscriber at the local rin 'ing key BK current to ringing current grounded pole or" alternate'contaet of the ontacts of the con and ack through the substation ringing key RIP. in upon actuationhas tact 163 opened, opening the iz-ing; circuit of relay 5% enthe upper Wii ding of the A the ground fr in the sleeve 9 non ext ided through the Ithe 5 id relay BS, the energized when the ring- '1 1C his tail,

ot' the supercurrent for encra! I lay 53inbeing fed the n Mi -tor 14L 3 conduc e plug Tl l to ground T The relay 151 .e rack upon c v a lock n circuit for the said i i atterr the 5 1 relay, its ern te consle lug n I l relay Sn" a es hole for the relay D traced from battery through the upger windrig or" the said relay coilduritor 1'11} alternate contact 140 of relay SR, conductors 1T2 and the sleeve if the trunk plug Tl? to ground at the sleeve of the iacl The opening of normal C01 tact 166 off he relay 161 hlinggs av-iont the ethicenient ot the holding signal HL'; Which ill alternate contact 177, normal co ct 170 of relay SR, conductors 172, 165 the sleeve or". the plug TP to ground at the slee e ot the jack J The closing of normal contact 170 of relay SR also establishes an energizing circuit for the disconnect re DR, traced irom battery through the winding of the saic relay DR, conductor 175. alternate contact 176 of the relay 1G1, conductor 17?, normal contact 170,:

conductors 1'72 and 165, the sleeve of the trunk plug; Tl? to ground at the sleeve of the jack J The relay upon energizing opens its normal contacts 180, 181, opening the con tinuity of the trunk conductors, and should the subscriber at the private branch exchange F recall, the removal of his receiver from the switchhook brings about the energization of the supervisory recall relay SE, traced from battery through the lower winding of the said relay SE, alternate contact 181 of relay DR, the ring contacts of the connected plug TP and jack J through the closed contacts of the switchhooh at the station F, back through the tip contacts of the connected plug TP and jack J through alternate contact 180 of relay DR, to ground through the upper winding oi. the said relay The relay SE upon ener mat-ion closes its alternate contact 182, which again lights the line lamp LL, to ground at alternate contact 182 of relay SE, notifying the operator, at the private branch exchange trunk PC that the substation F is recalling. The operator now actuates her listening key L1? to con nect her operators set to the trunk conductors, and to extend the connection to the main exchange she now withdraws the trunk plug T? from the jack J which Withdrawal opens the locking circuit of the relay 161, which allows the said relay to restore to normal. The closing (it normal contact 160 ot the relay 161 again closes an energizing circuit for relay DS over a path as previously described. Relay 161 upon de-energization also opens the energizing circuit of the relay D? at its alternate contact 176. The relay upon de-ener sjization opens its alternate contacts 180 and 1551, allowing the said supervisory recall relay SE to restore,

and the opening or its alternate contact 182 cllaces the line signal LL. The operator now again inserts the trunk plug Tl into tliejaclr J bringing about the energization of the supervisory relay SR and the relay 161, as previously described. The closing of normal contacts 180 and 181 of the relay DR now closes the continuity of the trunk conductors and extends the. said private branch xchange substation l? to the main exchange, ant the operation or the circuit from this point on is readily apparent from the previous description.

Should the operator wish to extend a conncction to a main automatic exchange, she

actuates her listening key Lll and the closure of alternate contact 185 of the ringin; key LK? extends ground to contacts 186 and 187 of the shunt springs of the calling device CD. The shunt springs 186 and 181 are closed, emendingthe ground from alternatc contact to the listening key Lil through the now closed contacts 186 and 18?, over conductor 188, tirough the winding of the trunk cut-oil relay CQR to battery. The closing otalternate contacts 189 and 190 of the relay COB now connects the calling device impulse springsover conductors 191 and 192, through alternate contacts 189 and 190, directly to theltrunlr conductors leading'to the main automatic exchange. After the called-tor party at the main automatic exchange has been selected and answers, the operation of the trunlr circuit PC is the same as previously described, and a further description of its operation is not deemed necessary.

The trunk PC, of course, is arranged so that the subscriber F can dial his own connection. 7 Connections can also be extended to the branch exchange while the plug is in a jack, without ringing the connected subscriber. In general, the circuit is capable of use. in establishing the same connections as more fully explained in connection with trunk circuit l C of Fig. 1.

Referring to Fig. 3, 300 represents an automatic substation, 301 an automatic switch;

302 an automatic connector switch, the bank terminals of the connector switch, and 303 either an automatic line switch or an automatic selector switch, PC* is the trunk circuit and F the private branch exchange substation. 0t course, any number of selectors may be inserted in the system accord ing to the size 01 the automatic exchange.

In working out;our invention We have employed preferred circuit arrangements all of which tend to make an eilicient operating system, but it is to be understood that va rious changes and modifications may readily be made without departing from the spirit and scope of our invention. Therefore, We do not'desire to be limited to the exact arrangement shown and described, but aim to cover all such changes and modifications as come within the spirit andscope of the appended claim.

What We c aim as new and desire to :secure by United States Letters Patent, is:

1. A telephone system including a calling and a called subscribefis line, a linkcircuit and a trunk circuit provided with a manually operable terminal for connecting said lines in conversational circuit, a disconnect signal and a calling signal for said trunlr circuit, and a relayior said trunk circuit controlled by one of said subscribers for au tomatically severing said trunk circuit to permit said trunk circuit to be used to 0peratesaid calling signal to indicate a call for a second connection before the manual terminal of said trunk circuit is disconnected from thesaid subscribers line. I

2. A telephone system including a link circuit and a trunk circuit provided with a manual terminal for interconnecting subscribers lines, and subscriber-controlled electromagnetic means for said trunk circuit for severing the talking conductors of the same when a subscriber signals ford-isconnection, and means for said trunk circuit for denoting a recall by the called subscriber.

3. A telephone system including a linl: circuit and a trunkcircuit provided with a manual terminal for interconnecting subscribe-rs lines, subscriber-controlled electromagnetic means for said trunk circuit for severing the talking conductors of the same when a subscriber signals for disconnection, means for said trunk circuit controlled by said electromagnetic means to permit a second call to be extended from said link circuit to said trunk circuitprior to the time that the manual terminal of the trunk oircuit is disconnected from the connected-With subscribers line.

A telephone system including a link circuit and a connecting circuit provided with a manual terminal for, interconnecting subscribers lines, subscriber controlled electromagnetic means for said connecting circuiti' or severing the talking conductors of the same when a subscriber signals tor disconnection, so that the subscriber Who is connected to the manual connecting circuit may use the connecting circuit to extend a call to said connecting circuit prior to the time that the manual terminal of the connecting circuit is disconnected from said subscribefis line, and means for said connecting circuit for denoting a-call by the called subscriber.

5. A telephone system. including :sub scribers lines, a link circuit and a manually controllable trunk circuit for interconnecting said subscribers lines, a signal for said trunk circuit at he board having said link circuit, subscriber automatically controllable means including a disconnect relay in said link circuit operable when the called subscriber signals for disconnection tor-opera tively disassoci'ating the called link circuit from the subscibers line, and means operable when the said called subscriber initiates a call to operate said signal at the board having the said link circuit to denote a call.

(i. r'i 'elephone sysl: 11 including sub scribers lines, a link circuit and a trunk circuit proi ided with a manual terminal Iior interconnecting said lines, a signal for said trunk circuit "operable when the link circuit is connected to the "trunk circuit to signal, the operator at the trunk board, a second signal for said trunk circuit operable when it is connected to called one of said sub scribers" lines, a disconnect signal, auto- "rat-ic means for severing the strands of the trunk circuit, and subscriber-controlled means "for operating said automatic means and said disconnect signal.

7. A telephone system including an A operators board and a B operatorvsboard, subscribers line's, alinl': circuit at the A operacors board and a truiilccir'cuit at the B operators board for effecting connection between said lines, automatic disconnect means in said trunk'cii'cuit for freeing the same when the called subscriber replaces his receiver, and subscriber controlled means operable to actuate a signal at the A operators board when the called subscriber initiates a call priorto the disconnection of the trunk circuit fromithe called 'sub'sc-ribers line. a y I 8. A telephone system including an A operators board and a B o em'wrs bom-d, subscribers lines, a link circuit at, the A? operators boa-rd and a trunk circuit at the B operators board for efiecti'ng connection between said lines, automatic disconnect means in said trunk circuit for freeing the same when the called subscriber replaces his receiver, a signal for said trunk circuit operable by .fhe Operator-at the A 'o'perators board to noti't'y the-B operator that second connection is desired priorto the disconnection of the manual iterinina'l of the trunk circuit from the called subscribers line, and 'a isignal for said trunk circuit at the A operators board for 'de noting a callby the subscriber at the B operators board. i

9. A telephone system including a calling subscribers line and a called subscribers line, an A operators board, a ll operators board, a link circuit for the A operators board and a trunk circuit tor the B operators board for interccni'iecting' said subscriberd lines, meansxvhereby the called subscriber may signal the operator the A operatofis board utter disconnection has been signaled for by the called subscriber, or the A operator may actuate ill) a signal at the B operators board prior to the time that the manual terminal in the trunk circuit is disconnected from the called subscribers line, disconnect supervisory means for said trunk circuit, and automatic means for said trunk circuit controlled by the called subscriber for operating said disconnect supervisory means, said automatic means also adapted to control contacts in the trunk conductors of said trunk circuit.

10. A telephone system including a calling subscribers line and a called subscribers line, an A operators board, a B operators board, a link circuit at the A operators board and a trunk circuit at the B operators board for efiecting a connection' between said subscribers lines, a signal at the A operators board actuatable by the B operator, disconnect means for said trunk circuit operable by the called subscriber for freeing said trunk circuit whereby the operator may again actuate said signal prior to the disconnection of the trunk circuit from the called subscribers line.

11. Atelephone system including a calling subscribers line and a called subscribers line, a cord circuit and a trunk circuit connecting said lines, a disconnect relay, and means operated by one of said subscribers When he signals for disconnection for operating said disconnect relay for disconnecting his line from the other of said subscribers lines, and for again efiecting an operation of said relay to connect the said subscribers line to the trunk circuit when the subscriber signals for a recall.

12. A telephone system including a calling subscribers line, a called subscribers line, a cord circuit and a trunk circuit for connecting said lines, a disconnect relay for dis-' connecting and connecting one of said subscribers lines and the conductors of said trunk circuit, subscriber controlled means for causing said relay to disconnect thecalled subscribers line from the conductors of the trunk circuit when the subscriber signals for disconnection and for causing said relay to connect the said subscribers line to the conductors of said trunk circuit when the subscriber signals for a recall.

13. A telephone system including a main exchange, a private branch exchange, a link circuit and a connecting circuit for extending a connection from a subscriber at the main exchange to a subscriber at the branch exchange, a'relay for said connecting circuit at the branch exchange, a second relay for said connecting circuit, means con trolled by the said private branch exchange subscriber for operating said first relay to disconnect his line from the trunk conductorsleading to the main exchange and for bridging the battery at the branch ex change across his line, whereby When he removes his receiver he energizes said second relay to cause the operation of said first relay to again connect his line to the main exchange over said trunk conductors.

1A. A telephone system including a main exchange, a private branch exchange, a link circuit and a connecting circuit for connecting a subscriber at the main exchange to a subscriber at the branch exchange, a relay for said connecting circuit controlled by the private branch exchange subscriber and operable to either connect the battery at the private branch exchange across the subscribers line or toconnect the battery at the main exchange across the subscribers line.

15. A telephone system including a main exchange, a private branch exchange, a link circuit for use in connecting a subscriber at the main exchange to a subscriber at the branch exchange, a relay controlling the connection of the subscriber at the private branch exchange with the subscriber at the main exchange, a relay controlled over the private branch exchange subscribers line for controlling said first relay, and a signal for said trunk circuit at the main exchange for denoting a call by the subscriber at the private branch exchange.

16. A telephone system including a calling subscribers line and a called subscribers line, a link circuit for use in connecting said subscribers lines, a relay controlling the connection of the calling subscribers line to the called subscribers line, and a relay controlled over one of said subscribers lines, said last relay being adapted when one of said subscribers replaces his receiver to operate said first relay to disconnect or disassociate said subscribers lines, said relay also being operable when said subscriber removes his receiver to again connect the subscribers lines.

17. A telephone system including a calling subscribers line and a called subscribers line, one of said subscribers lines being located in one exchange and the other of said subscribers lines being located in another exchange, manual means including trunks conductors for connecting said lines, a battery at each of said exchanges, and means controlled by one of said subscribers for bridging either of said batteries across his line.

Signed by us at Chicago, in the county of Cook and State of Illinois, this 16th day of September, 1920.

HIRAM D. Gunman. WILLIAM G. sHULL. 

